Finished Amnesia: The Bunker last night. Loved it. In terms of gameplay, I'd say this is Frictional's best work yet. I believe there was some news regarding the game being a roguelike (a genre I'm not particularly a fan of), but it's definitely not the case. The only random elements in the game are resources, codes & key items, which are randomized on every new playthrough; other than that, it's an open-ended but linear game.
It's more or less FG's attempt at creating an Alien: Isolation-like game. Sound plays a much bigger role here than in Alien, and is also your biggest enemy. I like how the game handled the time mechanic via the generator; it's a constant threat. Simply hiding until the beast goes away or moving too slowly isn't the most efficient way to go about exploring as you'll be burning through fuel fast. And if the generator goes off while you're deep in the bunker, then you're in for a ride. How the beast reacts to your defenses is also worth nothing. It obviously cannot be killed (until the end as an option), but trying to harm the beast in any way, whether that's through guns, explosives or traps will end up making it more aggressive and stronger. If the first encounter with the beast took one shot to stun it, then each subsequent encounter will require more shots to bring it down temporarily. This scales differently depending on the difficulty. The physics engine also really shines in this game, more so than FG's prior titles.
There are also some memorable small moments in the game. The Chapel & the Pillbox are my favourites. I won't go into them due to spoilers, and it's best to experience them on your own, but there is no safe place in the game, even on the outside. The Pillbox is a reminder that the protagonist is still in the middle of a war.
I did not come across any cheap jump-scares during my playthrough (compared to Rebirth which has a few) and is a pure psychological horror game through and through. If you are a fan of FG's previous games, namely SOMA, Amnesia: TDD, and Penumbra 1 & 2, then I highly recommend The Bunker.